Final answer:
The velocity of the body after 4 seconds is 12 m/s. The body will be 100 m from its starting point at approximately 8.16 seconds.
Step-by-step explanation:
(a) To find the velocity of the body after 4 seconds, we can use the formula: velocity = initial velocity + acceleration * time. Given that the body starts from rest and has a uniform acceleration of 3 ms-2, the initial velocity is 0. Plugging in the values, we have velocity = 0 + 3 * 4 = 12 m/s. Therefore, the velocity of the body after 4 seconds is 12 m/s. (b) To find when the body will be 100 m from its starting point, we can use the formula: displacement = initial velocity * time + 1/2 * acceleration * time^2. Since the body starts from rest, the initial velocity is 0. Plugging in the values, we have 100 = 0 * t + 1/2 * 3 * t^2. Simplifying the equation, we get t^2 = 100/1.5 = 66.67. Taking the square root of both sides, we get t = √66.67 ≈ 8.16. Therefore, the body will be 100 m from its starting point at approximately 8.16 seconds.